466 MONTGOMERY. [Vol. XV. 



substance of the vacuole stains more faintly than the ground 

 substance of the nucleolus, and has much the same color shade 

 as the nuclear sap. In certain germinal vesicles, which appear 

 to be of a somewhat later stage of development, numerous 

 small globules («.Z>., Figs. 306 and 310) are scattered through 

 the nuclear sap ; they stain with eosin a little more deeply than 

 the last-named nuclear portion, vary in number and size, and 

 have no regular distribution. In one case (Fig. 316), which 

 stood in a stage immediately antecedent to the pole spindle 

 formation, where there was a centrosome at either end of the 

 nucleus in the cytoplasm (the nuclear membrane had not yet 

 disappeared), such globules were present in the nucleus ; so 

 that we may infer that these globules are one of the latest 

 formations in the germinal vesicle before the pole spindle is 

 formed. I have not found any stages between the stage just 

 described and the perfectly formed spindle (Fig. 311). About 

 fifty or sixty ova were examined in the stage of the first pole 

 spindle, and in all of them the nucleolus had completely 

 disappeared, and no trace of it could be found either in the 

 nucleus or in the cytoplasm. 



What has been the manner of this disappearance of the 

 nucleolus .-* Its total disappearance must occur within a rela- 

 tively short time, since otherwise one would expect to find 

 stages showing this process. The observations which I was 

 able to make would demonstrate at least the mode of the com- 

 mencement of the vanishing of the nucleolus. We have seen 

 that when the germinal vesicle has attained its greatest size 

 or, in some cases, a little before its maximum size is reached, 

 its nuclear sap stains red ; therefore some substance must be 

 suspended in the caryolymph at this period which was not con- 

 tained in if before. Now such a substance must have been 

 derived either from other elements of the nucleus or from 

 the cytoplasm. It has probably not been derived from the 

 cytoplasm, since the nuclear membrane at this stage has its 

 maximum thickness and hence could not be easily penetrable ; 

 and also there is no appearance of any similar substance in the 

 cytoplasm, since no yolk globules or other nutritive elements 

 seem to be present, but the whole cytoplasm (at least the 



